The present invention relates generally to an optical system and electronic equipment that incorporates the same, and more particularly to a compact optical system and electronic equipment that uses such an optical system. The “electronic equipment” used herein, for instance, includes digital cameras, video cameras, digital video units, personal computers, mobile computers, cellular phones, and personal digital assistants.
Some optical systems with an image pickup optical unit comprising free-form surface prisms have already been proposed in the art.
In a typical optical system of this type, an axial light ray is defined by a light ray that propagates from the center of an object to the center of an image through the center of a stop, and reference planes are set for reflecting surfaces located obliquely to the optical axis of the optical system. Each reference plane is a plane defined by an axial chief ray incident on a certain reflecting surface and an axial chief ray reflected thereat. The reference plane exits for each reflecting surface.
One example is an optical system made up of two prisms that are provided separately or as a one piece, wherein all reference planes lie in one plane. In another optical system, thickness reductions are achieved by allowing light incident on prisms to be reflected three-dimensionally. However, all reference planes likewise lie in one plane. This optical system works as an image relay optical system.
In yet another optical system, too, light is reflected three-dimensionally. This optical system also works as an image relay optical system.